.TH bitesize 8  "2018-09-07" "USER COMMANDS"
.SH NAME
bitesize.bt \- Show disk I/O size as a histogram. Uses bpftrace/eBPF.
.SH SYNOPSIS
.B bitesize.bt
.SH DESCRIPTION
This can be used to characterize the distribution of block device
(disk) I/O sizes. To study block device I/O in more detail, see biosnoop(8).

This uses the tracepoint:block:block_rq_issue tracepoint, and is a simple
example of bpftrace.

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bpftrace.
.SH EXAMPLES
.TP
Trace block I/O and summarize as a histogram by process:
#
.B bitesize.bt
.SH FIELDS
.TP
0th
A process name (shown in "@[...]") is printed before each I/O histogram.
.TP
1st, 2nd
This is a range of I/O sizes, in Kbytes (shown in "[...)" set notation).
.TP
3rd
A column showing the count of I/O in this range.
.TP
4th
This is an ASCII histogram representing the count column.
.SH OVERHEAD
Since block device I/O usually has a relatively low frequency (< 10,000/s),
the overhead for this tool is expected to be low or negligible. For high IOPS
storage systems, test and quantify before use.
.SH SOURCE
This is from bpftrace.
.IP
https://github.com/iovisor/bpftrace
.PP
Also look in the bpftrace distribution for a companion _examples.txt file
containing example usage, output, and commentary for this tool.

This is a bpftrace version of the bcc tool of the same name.
.IP
https://github.com/iovisor/bcc
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Brendan Gregg
.SH SEE ALSO
biosnoop.bt(8)
